Anticorpos IgG direcionados a proteínas de membrana de hemácias e sua associação à anemia em infecções por Plasmodium vivax

Abstract

The destruction of uninfected erythrocytes is one of the leading causes of anemia in P. vivax infections. It has been estimated that about thirty-two non-parasitized red blood cells (RBCs) are destroyed for each parasitized RBC. Nevertheless, the molecules and the immunological mechanisms involved in the outcome of anemia during vivax malaria are still unknown. In this direction, the hypothesis investigated here is that autoantibodies induced to RBC membrane proteins are associated with this massive removal of uninfected RBC, leading to anemia in P. vivax infections. In order to answer this question, we used an immunoproteomic approach to elucidate differences in the global IgG response directed to on-infected RBCs proteins among sera from four distinct groups of individuals (i) healthy, (ii) non-infected with anemia by other etiologies, (iii) P. vivax infected patients without anemia and, finally, (iv) P. vivax infected patients with anemia. Proteins recognized by antibodies from these groups were identified by MALDI-ToF/ToF mass spectrometry. Distinct reactivity panels were detected, since antibodies from patients with vivax malaria reacted against a diverse antigen repertoire and this was even more evident in the anemic group. Sera from malaria patients recognized cytoskeleton proteins such as ankyrin, dematin, erythrocyte band 7 and protein 4.2. Furthermore, antibodies from malaria patients strongly reacted with spectrins, actin and band 3 protein. Sera from malaria anemic patients recognized these proteins even more strongly than sera from non-anemic infected individuals. Binding to band 3 was the most evident immunoproteomic result for the anemic patients with malaria. Aiming to determine whether high levels of such antibodies could be related to the sharing of antigens between the parasite and its host, we used bionformatics tools and showed that spectrins have a high sinteny with both P. vivax and host databases, highlighting the possible involvement of molecular mimicry in the production of high levels of antibodies in malaria. We also evaluate if anti-band 3 antibodies could change the geometric and mechanical properties of RBC membrane using defocusing microscopy. Interestingly, the non-infected RBC opsonization by anti-band 3 antibodies modified the RBC volume as well as the average of red cell surface membrane fluctuations, pointing to a decrease in red cell deformability. We speculate that this reduction could facilitate RBCs removal in the narrow capillary microcirculation. Our results clearly show that there is an association between anti-red blood cell antibodies and anemia in vivax malaria. Data generated here will contribute towards a better understanding of